This invention relates generally to drill booms and more particularly to a drill boom arrangement for positioning an elongated rock drilling apparatus to different drilling positions with respect to a boom support wherein the drill boom is pivotally connected to the boom support, a boom head carrying the elongated rock drilling apparatus is pivotally connected to the drill boom, and the rock drilling apparatus is rotatable about a geometrical polar axis which is parallel with the longitudinal direction of the rock drilling apparatus.
During drilling, a turning moment arises about the polar axis. In previously known drill booms of this type the turning moment is transferred to the drill boom through the turning device which rotates the rock drilling apparatus about the polar axis. The turning moment can be considerable, particularly in drill boom arrangements where the rock drilling apparatus is pivotable to a position which is substantially perpendicular to the polar axis.
It is an object of the invention to provide a drill boom of the above type in which the turning device does not need to be dimensioned to be able to transfer the whole turning moment. This means that the turning device can be smaller and less expensive. Another object of the invention is to provide a drill boom in which the turning moment is divided into two components; one component which is transferred to the drill boom through the turning device and one component which is transferred directly to the drill boom.
The above and other purposes of the invention will become obvious from the following description and from the accompanying drawings in which one embodiment of the invention is illustrated by way of example. It should be understood that this embodiment is only illustrative of the invention and that various modifications thereof may be made within the scope of the claims following hereinafter.